Display panel or portion thereof with a graphical user interface



The sole FIGURE is a front view of a display panel or portion thereof with a graphical user interface showing our new design.

The broken lines showing a portion of a display panel of a computing device, such as a personal computer, mobile phone, smart phone, personal digital assistant (PDA), tablet, television device, media player, or other computing device, are included for the purpose of illustrating environmental structure and form no part of the claimed design. The other broken lines in the figures and the areas within the broken lines show portions of the graphical user interface that are included for illustrative purposes and form no part of the claimed design. 

CLAIM The ornamental design for a display panel or portion thereof with a graphical user interface, as shown and described. 